# [−][src]Struct cstr_core::CStr

    pub struct CStr { /* fields omitted */ }

Representation of a borrowed C string.

This dynamically sized type is only safely constructed via a borrowed version of an instance of `CString`. This type can be constructed from a raw C string as well and represents a C string borrowed from another location.

Note that this structure is not `repr(C)` and is not recommended to be placed in the signatures of FFI functions. Instead safe wrappers of FFI functions may leverage the unsafe `from_ptr` constructor to provide a safe interface to other consumers.

# Examples

Inspecting a foreign C string:

ⓘThis example is not tested

    use cstr_core::CStr;
    use cstr_core::c_char;

    extern { fn my_string() -> *const c_char; }

    unsafe {
        let slice = CStr::from_ptr(my_string());
        println!("string length: {}", slice.to_bytes().len());
    }

Passing a Rust-originating C string:

ⓘThis example is not tested

    use cstr_core::{CString, CStr};
    use cstr_core::c_char;

    fn work(data: &CStr) {
        extern { fn work_with(data: *const c_char); }

        unsafe { work_with(data.as_ptr()) }
    }

    let s = CString::new("data data data data").unwrap();
    work(&s);

Converting a foreign C string into a Rust `String`:

ⓘThis example is not tested

    use cstr_core::CStr;
    use cstr_core::c_char;

    extern { fn my_string() -> *const c_char; }

    fn my_string_safe() -> String {
        unsafe {
            CStr::from_ptr(my_string()).to_string_lossy().into_owned()
        }
    }

    println!("string: {}", my_string_safe());

## Methods

### `impl CStr`[src]

#### `pub unsafe fn from_ptr<'a>(ptr: *const c_char) -> &'a CStr`[src]

Casts a raw C string to a safe C string wrapper.

This function will cast the provided `ptr` to the `CStr` wrapper which allows inspection and interoperation of non-owned C strings. This method is unsafe for a number of reasons:

- There is no guarantee to the validity of `ptr`.
- The returned lifetime is not guaranteed to be the actual lifetime of `ptr`.
- There is no guarantee that the memory pointed to by `ptr` contains a valid nul terminator byte at the end of the string.
- It is not guaranteed that the memory pointed by `ptr` won't change before the `CStr` has been destroyed.

> Note: This operation is intended to be a 0-cost cast but it is currently implemented with an up-front calculation of the length of the string. This is not guaranteed to always be the case.

# Examples

ⓘThis example is not tested

    use cstr_core::CStr;
    use cstr_core::c_char;

    extern {
        fn my_string() -> *const c_char;
    }

    unsafe {
        let slice = CStr::from_ptr(my_string());
        println!("string returned: {}", slice.to_str().unwrap());
    }

#### `pub fn from_bytes_with_nul(bytes: &[u8]) -> Result<&CStr, FromBytesWithNulError>`[src]

Creates a C string wrapper from a byte slice.

This function will cast the provided `bytes` to a `CStr` wrapper after ensuring that it is null terminated and does not contain any interior nul bytes.

# Examples

    use cstr_core::CStr;

    let cstr = CStr::from_bytes_with_nul(b"hello\0");
    assert!(cstr.is_ok());

Creating a `CStr` without a trailing nul byte is an error:

    use cstr_core::CStr;

    let c_str = CStr::from_bytes_with_nul(b"hello");
    assert!(c_str.is_err());

Creating a `CStr` with an interior nul byte is an error:

    use cstr_core::CStr;

    let c_str = CStr::from_bytes_with_nul(b"he\0llo\0");
    assert!(c_str.is_err());

#### `pub unsafe fn from_bytes_with_nul_unchecked(bytes: &[u8]) -> &CStr`[src]

Unsafely creates a C string wrapper from a byte slice.

This function will cast the provided `bytes` to a `CStr` wrapper without performing any sanity checks. The provided slice must be null terminated and not contain any interior nul bytes.

# Examples

    use cstr_core::{CStr, CString};

    unsafe {
        let cstring = CString::new("hello").unwrap();
        let cstr = CStr::from_bytes_with_nul_unchecked(cstring.to_bytes_with_nul());
        assert_eq!(cstr, &*cstring);
    }

#### `pub fn as_ptr(&self) -> *const c_char`[src]

Returns the inner pointer to this C string.

The returned pointer will be valid for as long as `self` is and points to a contiguous region of memory terminated with a 0 byte to represent the end of the string.

WARNING

It is your responsibility to make sure that the underlying memory is not freed too early. For example, the following code will cause undefined behavior when `ptr` is used inside the `unsafe` block:

    use cstr_core::{CString};

    let ptr = CString::new("Hello").unwrap().as_ptr();
    unsafe {
        // `ptr` is dangling
        *ptr;
    }

This happens because the pointer returned by `as_ptr` does not carry any lifetime information and the string is deallocated immediately after the `CString::new("Hello").unwrap().as_ptr()` expression is evaluated. To fix the problem, bind the string to a local variable:

    use cstr_core::{CString};

    let hello = CString::new("Hello").unwrap();
    let ptr = hello.as_ptr();
    unsafe {
        // `ptr` is valid because `hello` is in scope
        *ptr;
    }

#### `pub fn to_bytes(&self) -> &[u8]`[src]

Converts this C string to a byte slice.

This function will calculate the length of this string (which normally requires a linear amount of work to be done) and then return the resulting slice of `u8` elements.

The returned slice will not contain the trailing nul that this C string has.

> Note: This method is currently implemented as a constant-time cast, but it is planned to alter its definition in the future to perform the length calculation whenever this method is called.

# Examples

    use cstr_core::CStr;

    let c_str = CStr::from_bytes_with_nul(b"foo\0").unwrap();
    assert_eq!(c_str.to_bytes(), b"foo");

#### `pub fn to_bytes_with_nul(&self) -> &[u8]`[src]

Converts this C string to a byte slice containing the trailing 0 byte.

This function is the equivalent of `to_bytes` except that it will retain the trailing nul instead of chopping it off.

> Note: This method is currently implemented as a 0-cost cast, but it is planned to alter its definition in the future to perform the length calculation whenever this method is called.

# Examples

    use cstr_core::CStr;

    let c_str = CStr::from_bytes_with_nul(b"foo\0").unwrap();
    assert_eq!(c_str.to_bytes_with_nul(), b"foo\0");

#### `pub fn to_str(&self) -> Result<&str, Utf8Error>`[src]

Yields a `&str` slice if the `CStr` contains valid UTF-8.

This function will calculate the length of this string and check for UTF-8 validity, and then return the `&str` if it's valid.

> Note: This method is currently implemented to check for validity after a constant-time cast, but it is planned to alter its definition in the future to perform the length calculation in addition to the UTF-8 check whenever this method is called.

# Examples

    use cstr_core::CStr;

    let c_str = CStr::from_bytes_with_nul(b"foo\0").unwrap();
    assert_eq!(c_str.to_str(), Ok("foo"));

## Trait Implementations

### `impl Debug for CStr`[src]

#### `fn fmt(&self, f: &mut Formatter) -> Result`[src]

Formats the value using the given formatter. Read more

### `impl PartialEq<CStr> for CStr`[src]

#### `fn eq(&self, other: &CStr) -> bool`[src]

This method tests for `self` and `other` values to be equal, and is used by `==`. Read more

#### `
#[must_use]
fn ne(&self, other: &Rhs) -> bool` 1.0.0[src]

This method tests for `!=`.

### `impl Eq for CStr`[src]

### `impl Ord for CStr`[src]

#### `fn cmp(&self, other: &CStr) -> Ordering`[src]

This method returns an `Ordering` between `self` and `other`. Read more

#### `fn max(self, other: Self) -> Self` 1.21.0[src]

Compares and returns the maximum of two values. Read more

#### `fn min(self, other: Self) -> Self` 1.21.0[src]

Compares and returns the minimum of two values. Read more

#### `fn clamp(self, min: Self, max: Self) -> Self`[src]

🔬 This is a nightly-only experimental API. (`clamp`)

Restrict a value to a certain interval. Read more

### `impl PartialOrd<CStr> for CStr`[src]

#### `fn partial_cmp(&self, other: &CStr) -> Option<Ordering>`[src]

This method returns an ordering between `self` and `other` values if one exists. Read more

#### `
#[must_use]
fn lt(&self, other: &Rhs) -> bool` 1.0.0[src]

This method tests less than (for `self` and `other`) and is used by the `<` operator. Read more

#### `
#[must_use]
fn le(&self, other: &Rhs) -> bool` 1.0.0[src]

This method tests less than or equal to (for `self` and `other`) and is used by the `<=` operator. Read more

#### `
#[must_use]
fn gt(&self, other: &Rhs) -> bool` 1.0.0[src]

This method tests greater than (for `self` and `other`) and is used by the `>` operator. Read more

#### `
#[must_use]
fn ge(&self, other: &Rhs) -> bool` 1.0.0[src]

This method tests greater than or equal to (for `self` and `other`) and is used by the `>=` operator. Read more

### `impl Hash for CStr`[src]

#### `fn hash<__H: Hasher>(&self, state: &mut __H)`[src]

Feeds this value into the given [`Hasher`]. Read more

#### `fn hash_slice<H>(data: &[Self], state: &mut H) where
H: Hasher,` 1.3.0[src]

Feeds a slice of this type into the given [`Hasher`]. Read more

### `impl AsRef<CStr> for CStr`[src]

#### `fn as_ref(&self) -> &CStr`[src]

Performs the conversion.

### `impl<'a> Default for &'a CStr`[src]

#### `fn default() -> &'a CStr`[src]

Returns the "default value" for a type. Read more

## Auto Trait Implementations

### `impl Send for CStr`

### `impl Sync for CStr`

## Blanket Implementations

### `impl<T> Borrow<T> for T where
T: ?Sized,` [src]

#### `fn borrow(&self) -> &T`[src]

Immutably borrows from an owned value. Read more

### `impl<T> BorrowMut<T> for T where
T: ?Sized,` [src]

#### `fn borrow_mut(&mut self) -> &mut T`[src]

Mutably borrows from an owned value. Read more

### `impl<T> Any for T where
T: 'static + ?Sized,` [src]

#### `fn type_id(&self) -> TypeId`[src]

Gets the `TypeId` of `self`. Read more

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